In May 2012 and May 2016, our 2002 Stock Incentive Plan was amended to increase the number of shares available for issuance by 1.8 million and 0.9 million shares, respectively. As of December 31, 2018, there were 0.6 million shares available for future option grants or direct issuance under the Amended 2002 Plan.

Following is a summary of our stock option plan activity and related information:

Shares

Weighted

Average

Exercise

Price

Weighted

Average

Remaining

Contractual

Term in

Years

Aggregate

Intrinsic

Value

(In thousands)

Balance at December 31, 2017

1,876,332

$

53.17

5.77

$

157,340

Granted

228,362

162.00

Exercised

(358,162)

55.24

Forfeited

(10,228)

114.53

Balance at December 31, 2018

1,736,304

66.71

5.47

125,858

Exercisable at December 31, 2018

1,313,374

47.03

4.56

117,314

Options vested and expected to vest as of December 31, 2018

1,734,304

$

66.71

5.47

$

125,858

The weighted-average grant-date fair value of all stock options granted during 2018, 2017 and 2016 was $66.71, $53.17 and $46.53 per share, respectively. The total intrinsic value of all options exercised during 2018, 2017 and 2016 was approximately $51.9 million, $13.3 million and $12.0 million, respectively.

Cash received from options exercised, net of fees paid, in 2018, 2017 and 2016 was $19.8 million, $4.7 million and $6.2 million, respectively.

Following is a further breakdown of the options outstanding as of December 31, 2018:

Range of exercise prices

Options

outstanding

Weighted

average

remaining life

in years

Weighted average

exercise price

Options

exercisable

Weighted average

exercise price

$8.58 - $10.05

184,702

1.87

$

10.00

184,702

$

10.00

$10.12 - $12.81

46,510

2.92

11.40

46,510

11.40

$14.47 - $14.47

217,616

3.11

14.47

203,616

14.47

$16.14 - $17.88

38,790

0.17

16.36

38,790

16.36

$21.92 - $21.92

200,372

4.13

21.92

200,372

21.92

$32.00 - $56.26

182,767

5.70

50.38

174,470

50.10

$63.58 - $67.53

20,434

5.44

67.42

20,153

67.47

$74.42 - $74.42

190,825

5.12

74.42

190,825

74.42

$85.79 - $100.38

299,282

7.57

93.32

157,872

91.62

$101.15 - $195.91

353,006

8.79

148.50

96,064

131.77

1,734,304

5.47

$

66.71

1,313,374

$

47.03

The assumptions used for the specified reporting periods and the resulting estimates of weighted-average grant date fair value per share of options granted:

Year Ended December 31,

2018

2017

2016

Risk-free interest rate

2.7%-3.0%

2.0%-2.2%

1.3%-1.9%

Expected volatility

33%-36%

43%-47%

48%-50%

Expected term

5.1 to 5.8 years

6.5 to 6.8 years

6.6 to 6.7 years

As of December 31, 2018, there was $20.4 million of total unrecognized compensation cost related to non-vested stock options. That cost is expected to be recognized over a weighted average period of 2.39 years.

Restricted Stock Activity

The following is a summary of our restricted stock activity and related information:

Shares

Weighted-Average

Grant Date Fair

Value

Outstanding at December 31, 2017

133,294

$

91.60

Granted

62,133

169.92

Vested

(61,989)

86.19

Forfeited

(1,165)

125.16

Outstanding at December 31, 2018

132,273

$

130.63

As of December 31, 2018, unrecognized compensation cost related to non-vested stock awards amounted to $9.2 million. That cost is expected to be recognized over a weighted average period of 1.38 years.

Employee Stock Purchase Plan

As of December 31, 2018, 64,008 shares of our common stock are available for future issuance under the Amended Employee Stock Purchase Plan, or ESPP. The ESPP permits eligible employees to purchase up to 1,250 shares of Ligand common stock per calendar year at a discount through payroll deductions. The price at which stock is purchased under the ESPP is equal to 85% of the fair market value of the common stock on the first of a six month offering period or purchase date, whichever is lower. There were 3,386, 3,061 and 1,961 shares issued under the ESPP in 2018, 2017 and 2016, respectively.

Share Repurchases

In May 2018, in conjunction with our 2023 Notes debt offering, we repurchased 260,000 shares of our common stock at a cost of $191.14 per share. In September 2018, the board of directors authorized us to repurchase up to $200.0 million of our common stock from time to time over a period of up to three years (the “Repurchase Program”). As of December 31, 2018, $125.2 million remains available for repurchase under the authorized program. On January 23, 2019, the board of directors elected to increase the Repurchase Program, authorizing us to repurchase up to a maximum of $350.0 million of our outstanding common stock under the Repurchase Program. The Repurchase Program will expire, as originally scheduled, on September 20, 2021. Since December 31, 2018 and as of February 28, 2019, we acquired 400,177 additional shares during 2019, and the maximum dollar value of shares that may yet be purchased under the Repurchase Program was $225.9 million.During the years ended December 31, 2018, 2017 and 2016, we repurchased 782,248 shares for $127.5 million, 14,000 shares for $2.0 million, and 40,500 shares for $3.9 million, respectively.

The entire disclosure for shareholders' equity comprised of portions attributable to the parent entity and noncontrolling interest, including other comprehensive income. Includes, but is not limited to, balances of common stock, preferred stock, additional paid-in capital, other capital and retained earnings, accumulated balance for each classification of other comprehensive income and amount of comprehensive income.